The present invention relates to a synchronizer of transmission for vehicles and, more particularly, to a simplified synchronizer for reversing in manual transmission.
In general, no synchronizer is provided for the reverse operation of a transmission of an automobile or the like vehicle. Therefore, in quick shifting or in shifting to reverse position while the vehicle is running ahead at a low speed, the gears sound to unsmooth the shifting operation. On the other hand, it is a current tendency to decrease the internal resistance of transmission through reduction of the viscosity of lubricating oil and to decrease the drag torque by the use of antifriction bearings, in order to cope with demands for smaller manipulating force and reduction in fuel consumption. As a result, when the clutch is operated from on state to off state while the automobile is stopped with its transmission selecting the neutral state, the rotating shafts such as input shaft are not decelerated immediately so that gear sounds to unsmooth the shifting operation for reversing. In the transmission of the kind described, therefore, it is necessary to take a suitable countermeasure for obviating the problem of unsmooth shifting to reverse position.
If the reverse gear train is of synchromesh tupe, the above-mentioned problem will be overcome by applying a synchronizer similar to those of forward gears. This, however, is accompanied by the following two problems.
Firstly, it is to be pointed out that, since the reverse gear rotates in the direction opposite to the direction of rotation of the output shaft, an extremely high relative sliding rotation speed is developed between the reverse gear and the output shaft during forward running of the automobile. It is, therefore, necessary to pay specific attention and to take necessary measure for preventing seizure between the reverse gear and the output shaft, resulting in a raised cost of production uneconomically. Secondly, continuous meshing between the reverse gear and reverse idler gear causes various problems or inconveniences such as increased drag resistance in the transmission, generation of noises in the neutral state of the transmission, reduction in the efficiency, deterioration in the shift feeling due to an increase of the moment of inertia during shifting between forward gears and so forth. To obviate the problems arising from the continuous meshing between the reverse gear and reverse idler gear, it is preferred to adopt a selective sliding type reverse gear train in which the reverse idler gear or the reverse gear is slidable. This type of gear train, however, inconveniently necessitates various additional synchromesh parts such as synchronizer ring, shifting key and so forth.